出版社：American Society for Biochemistry and Molecular Biology
摘要：Apolipoprotein C-III (apoC-III) is an important regulator oflipoprotein metabolism. Radioisotope and stable isotope kineticstudies show differing results in relation to the kinetics ofapoC-III in HDL. Kinetic analysis of HDL apoC-III may be difficultbecause of its low concentration, as well as the presence ofother apoproteins at higher concentration, in the HDL fraction.We used Intralipid® (IL), known to preferentially extractapoC proteins from plasma, as a means of extracting apoC-IIIfrom HDL before apoprotein separation by isoelectric focusinggel electrophoresis for the measurement of tracer enrichment.Protein purity was assessed by an isoleucine-to-leucine (Ile/Leu)ratio, as apoC-III contains no isoleucine. We compared apoC-IIIkinetics in 14 men using a bolus infusion of deuterated leucine.The Ile/Leu ratio for IL-extracted HDL (IL-HDL) apoC-III (3.0± 0.7%) was not different from that of VLDL apoC-III(2.6 ± 0.6%) but was significantly lower than that ofuntreated HDL apoC-III (9.0 ± 2.9%) (P < 0.001). Theisotopic enrichment curves and fractional catabolic rates (FCRs)for IL-HDL apoC-III were not different from those of VLDL apoC-III.In contrast, HDL apoC-III had significantly lower isotopic enrichmentsand FCRs than IL-HDL apoC-III (P < 0.001). In conclusion,this simple IL method can be used to isolate apoC-III from HDLwith minimal interference from other HDL apoproteins, and itdemonstrates that the kinetics of apoC-III in VLDL and HDL aresimilar, supporting the concept of a single kinetically homogeneouspool of apoC-III in plasma.Supplementary key words high density lipoprotein • very low density lipoprotein • gas chromatography-mass spectrometry • lipoprotein metabolism • apolipoprotein C-III
Abbreviations: apoC-III, apolipoprotein C-III; d3-leucine, deuterated leucine; FCR, fractional catabolic rate; IEF, isoelectric focusing; IL, Intralipid®; Ile/Leu, isoleucine-to-leucine; PR, production rate; PVDF, polyvinylidene difluoride; TRL, triglyceride-rich lipoprotein; TTR, tracer-to-tracee ratio
